The purpose of this study was to address 3 short term objectives; (1) Determine the effects of physiologic testosterone (T) therapy on neurological function and functional independence following traumatic brain injury (TBI) in hypogonadal men during inpatient rehabilitation; (2) Document the natural history of neuroendocrine dysfunction and recovery in men during inpatient rehabilitation after TBI; (3) Obtain data to validate the NIH toolbox, a novel assessment of neurological function for use in the TBI population; and 2 long-term objectives: (1) Utilize study findings to design a multicenter trial to further assess the impact of T therapy in hypogonadal men following TBI and (2) Impact TBI practice management with new information about neuroendocrine dysfunction after TBI and hormone treatments to improve outcomes.

This randomized, double blind, placebo-controlled pilot study assessed the hormonal status of men on admission to an inpatient TBI rehabilitation program. 498 consecutively admitted men for TBI rehabilitation were screened for participation in the study. 22 participants with low T who met all criteria were randomized into placebo (n=10), or physiologic T therapy (n=12). Of those with normal T who met all criteria, 24 were randomized into a follow up group. All participants were evaluated every two weeks for up to 12 weeks: hormone levels, FIM ratings and NIH Toolbox testing as able. There was participant drop out over time as participants were discharged from the hospital. The final analysis examined differences between the normal T, low T Treatment and low T placebo groups on hormone levels, FIM ratings and NIH Toolbox results at baseline and weeks 2, 4 and 6.

Inclusion Criteria:

1. History of TBI as defined as "damage to brain tissue caused by an external mechanical force as evidenced by loss of consciousness or post traumatic amnesia (PTA) due to brain trauma or by objective neurological findings that can be reasonably attributed to TBI on physical examination or mental status examination;"82

2. Moderate to severe TBI as indicated by a Glasgow Coma Scale (GCS) score of less than or equal to 12 at emergency department admission, or post traumatic amnesia (PTA) of greater than or equal to seven days post-injury, or radiographic evidence of intracranial injury;

3. Continuously hospitalized from time of injury until admission for rehabilitation;

4. Enrolled in study within 6 months of TBI;

5. Receiving inpatient rehabilitation for TBI at Craig Hospital;

6. Males between the ages of 16 to 65 (inclusive);

7. Approval by attending physician;

8. Testosterone level below the assay normal range;

9. Consent to study participation

   Exclusion Criteria:

10. History of any conditions that would prohibit testing contained in the NIH toolbox;

11. Non-English or non-Spanish speaking (to the extent that would limit the ability to complete study measures);

12. History of prior psychiatric illness requiring hospitalization;

13. Prior testosterone therapy;

14. History of or current or suspected hormonally dependent cancer , including carcinoma of the breast or prostate cancer;

15. Known hypersensitivity to any T gel ingredients including alcohol and soy products;

16. Hematocrit (HCT) greater than 55% (normal range in Colorado is up to 52) or transaminase elevation >4x upper limit of the normal range.

17. Abnormal finding on digital rectal examination such as nodule, asymmetry, or induration (Does not include enlarged prostate or abnormal rectal tone)

18. PSA>4.0

19. BMI <16 or >40kg/m2

20. History of untreated prolactinoma

21. History of severe heart failure or uncontrolled medical problem that would interfere with the participant's safety in the study as determined by the investigator.

1 administrative withdrawal in Normal T Followed group making the total followed 46.